Injection molding apparatus



Nov. 14, 1944. w cousmo 2,362,469

INJECTION MOLDING AFFARATUS Filed Sept 10, 1941 lNVENTOR hzli'er 2 61 01152270.

ATTORNEYSS.

Patented Nov. 14, 1944 UNITED STATES INJECTION MOLDING APPARATUS Walter P. Cousino. Detroit, Mich, assignor to Ohrysler Corporation, Highland Park, Mich a corporation of Delaware Application September 10, 1941, Serial No. 410,233 comics. (0!; 1s-so;

This invention relates to on improved plastic injection molding apparatus. One of the main objects of the inventionis the provision in apparatus of this kind of mechanism for displacing plastic material under compression which does not require close fits and tolerances oi! the order necessary in cylinder and piston pump ti l-l8 plastic displacing apparatus of conventional construction. A

Another object of the invention is to provide plastic displacing mechanism in iniection molding apparatus of this character whichlsss displacing plunger that operates in confined relation throughout only a small increment oi? its stroke with the wells 01 the passage from which it displaces plastic material.

A further object of the invention is to provide injection molding apparatus of this kind from which may be efiectively injected into a mold charges oi plastic material comprising in their solid state mixtures of diverse particle sizes including plastic dust, grains and larger irng merited particles oi scrap plastic-like material.

A still further object 01' the invention is to provide s. plastic displacing" jin'it'dii injection molding of this kind which is adapted 'to'displace from the nozzle of the apparatus a continuous stream oi plastic-like material of moldable consistency.

An additional object of the invention is the 30 provision of means'in injection molding apparatus for utilizing the plastic material to produce, during the returnstrokeof the displacing element, a seal'at theinlet end of the nozzle tic discharged therefrom may governed; to proviso interconnecting mechanism between the above mentioned control valve and an operatin control for the displacing mechanism, by which the'punsp is started when the valve is opened endstopped when the valve is closed; and to pro vine means for heating the plastic during its passage through" the nozzle to a state of free flowing moidahle consistency.

T Inidditional object o! the invention is the provision of injection molding apparatus which is adapted to'iniect plastic-like materials of diverse kinds including thermoplastic andthermcsetting plastic materials as well as rubber and synthetic rubber compounds.

An illustrative embodiment oi the invention is shown in the accompanying drawing in which:

Fig. i is a side elevstional view, partly in section, of injection molding apparatus embodying the invention. V V V Fig; 219 's'irsgrnentary vertical sectional view oi the plastic dlschsrge'glfil some structure of the molding apparatus shown in'Fig. 1. V

Figrsis n iragmentary side elevations} view of'the'dischcrgirfi oi the nozzle structure. 7

Fig. i'is'a consents: sectional view taken on the fine t; oi Fig. 2.

In Fig. 1 of the drawing is illustrated diagrammatically e molding apparatus embodying the invention which includes a support in having a mold secticiffi attached to one end thereof. A cooperative mold section I! is carried by a piston red I: having a piston H at its right extremity reciprocably mounted in a cylinder l5.

through which the 'plsstic is discharged into a 85 The interior of the cylinder i5 is communicalnold.

Another object oi" the invention is the provision oi displacing and discharging apparatus of kind by which plastic 'nrsterials, including rub ber, may be dispiaced through extruding operation.

Other objects of the invention are to provide cooling and heatzinsulating means at the outlet end or a plastic displacing device of this kind" which facilitates the retention of the last incre of work by exhausting the fluid medium through ments 01' plastic operated upon by a displacing element in a compressed cake-like formatiun' of substantially unfused solid particles between suecessive strokes of the displacing elements; to

provide an abutment at the junction oi the dis- 7 to charge nozzle and pump portion of apparatus cl 7 this character against which the cake-like formotion of plastic-like particles seats to form a seal; to provide a control valve at the outlet 0. die m undo tively connected'by'pipes i8 and "with a source uncompressed air or other fluid under pressure inot shown). The fluid medium may be supoliertthrough the pipe "to the right end porol the cylinder IS in order to forcefully noldfitlie' nold section I! in operstive contact wlth'the'niold section H. The mold section I! if s"; hdrawn from the mold section il in order tocccomniodate removal cine molded piece the pipe 11 and admitting fiuid under pressure into the left end of the cylinder I! through the pipe it. The particular mold supporting and operating structure is shown in the drawing as indicative onlg oi pne iorm of mold structure with which my improved plastic injection mechanism is adapted to be employed, it being understeod that various types of mold supporting end 0! the n zzl y which the quantity 0! piasas and operating devices may be used while obtaining the benefits and advantages of the improved injection apparatus.

when the mold sections ii and II are in operative contacting relationship, there is provided a conical gate ll having a tapered inlet portion ll against which the nomle, generally designated by the numeral It. is adapted to seat in order to deliver plastic-like material to the interior of the mold. In the form of the invention shown in the drawing. the nozzle it moves a body portion 2| in which are formed two axially extending es 2! and a which are joined at their lower extremity and which communicate with an outlet e It formed in the discharge end of the nomle. A valve 24' having an operating lever 25' is provided in the discharge passage It ior the purpose of controlling the flow of moldable plastic material into the mold. Mounted on the upper extremity of the nozzle body portion II is a hopper is which is preferably heat insulated from the body portion of the nozzle by a layer of insulating material It. Satisfactory insulation of the hopper from the nozzle may be. eil'ected by providing a deep groove between the nozzle and hopper structures and leaving only a narrow ring of metal directly therebetween in order to space the main portions of the nozzle and hopper apart.

Formed in the lower extremity of the hopper 26 is a transverse wall 21 having passageways 2| and II formed therein which are aligned with the passages 22 and 23. respectively. of the no:- zle. Both the nozzle ea 22 and 28 and the passageways 28 and Is at the lower extremity of the hopper are of generally rectangular shape having rounded extremities as illustrated in Fig. 4. At least the widths of the passages 22 and II are formed to greater dimensions than the corresponding widths of the es 2! and II in order to provide abutments or shoulders II and II at the outlet ends of the eways I8 and a. respectively. The cross sectional lengths or the rectangular passageways I! and It may also, if desired, exceed the corresponding cross sectional lengths of the passageways 28 and ll in order to provide abutments or shoulders at the extremities of the cross section of the outlet ends oi the passageways 28 and 2.. The abutments II and Ii face away from the interior of the hopper II and, as hereinafter more clearly set forth, cooperate with the plastic material in performing a self-sealing action which prevents the reverse flow of plastic material from the norzle and into the hopper. Disposed in the hopper 28 is plastic displacing mechanism. generally designated by the numeral II, which includes a body portion as having guideways II and 38 in which are reciprocably mounted plungers II and 81. The plungers it and u are aligned with the passageways 2t and so and are so shaped as to extend therethrough in relatively loose fitting relation with respect to the walls of the latter passageways. Formed on the adjacent sides of the plungers it and II are rack teeth I! and ll which are meshed with the teeth of a pinion l iournalled in the body structure 33 at a location between the plungers 88 and 81. The plunger II is operatively connected by a ring II with a lever l2 pivotally mounted at 43 on a support 44. The lever 42 may be oscillated by any suitable operating mechanism in order to reciprocate the plunger 38 which is in turn geared through the pinion so to the rack teeth ll of the plunger 31 in such a relation as to cause the latter plunger to be returned from a discharge stroke when the plunger It is urged downwardly through its discharging stroke. The plunger II is thus urged downwardly through its discharge stroke while the plunger Cl is being moved upwardly by the lever 4!.

For th purpose of illustration, there is shown in Fig. 1 an operating mechanism comprising a reciprocating air motor ll having a cylinder 4| provided with a piston 11 which is connected by a piston rod ll with the left extremity of the lever 42. Air is alternately supplied to and exhausted from respectively opposite ends of the cylinder ll under the control of suitable valve mechanism with which reciprocating air motors of this kind are conventionally provided. Air or other fluid medium under pressure is fed to the motor through a conduit as in which is provided a control valve ll having an operating lever II.

The major portions of the reciprocative stroke of the plungers II and II occur within the unconfined space in the hopper II which is normally filled with solid particles of plastic-like material. Only the lower end portions of these plungert extend into and travel in the passageways 28 and 2!. Thus. the plungers operate in confined relation with respect to the walls of the passages II and II throughout only short effective strokes. Inasmuch as the major portions or the respective strokes of the plungers occur in the hopper and with the plungers II and 81 so geared together by the pinion III as to cause one plunger to be located at the upper limit of its stroke while the other plunger is located at the lower limit of its stroke, as shown in Fig. 1, one plunger is moved throughout a substantial part oi the hopper portion of its stroke alter the other plunger has been withdrawn from the passageway with which it is alined. Therefore. the movement oi. one plunger through the hopper agitates the plastic-like material while the other plunger is withdrawn from its alined passageway, thereby assuring the flow of plastic-like material into the latter passageway preparatory to the next successive discharge therefrom. Each time one of these plungers is projected into its associated passage in the bottom wall of the hopper, it displaces i'rom the hopper an increment of the charge of solid particles of plastic-like material and compresses this increment of the charge into a solid cake-like formation which seats against the shoulders or abutments II and ii to provide a seal at the outlet end of the eway for preventing reverse flow of plastic material from the nozzle back into the hopper. Thus, while one plunger is undergoing its return stroke, the cakelike formation of solid particles of plastic-like material acts as a valve or seal until the plunger is again propelled through its discharge stroke to project another increment of the charge into the nozzle and to thus produce another cake-like formation of solid particles of plastic-like material. Since the plastic-like material itself serves this sealing function, it is not necessary to have a close fitting relationship between the sides of the plungers and the walls of the passages II and is in which they operate nor is it necessary to employ mechanical valve mechanism of any i kind for maintaining under compression plastic previously fed to the passages 22 and II of the nozzle. 7

In order to convert the solid particles of plastic-like material to a flowable state of moldable consistency, heat is applied to the nozzle throughout its main length by heating elements, generally deslgnated by the numeral 82. These heating elements may comprise coils of an electrical retic-like material.

7 In the injection molding oi thennoplastic msinsulation 2! also serves to'prevent direct and exclusive transmission or heat from the hassle to the wall structure of the hopper in which the passages and I! are formed and adjacent which the foregoing seals are produced by the cake-like formations 23 of solid particles of plas- Cooling medium is circulated through the cored out passages of the bottom wall 21 or the hopper by inlet and outlet pipes 55 and II respectively. 7

During operation 01' the foregoing piasticmolding apparatus, it is not necessary to employ the control valve 24 for the purpose of cutting 01! the discharge of plastic material from the hopper tor the fluid pressure applied on the reciprocating motor it may be predetermined to produce a desired degree of compression upon the plastic material in the mold and after the mold has been filled and the plastic material therein compressed to a predetermined extent, the back pressure exerted through the plastic may, ii desired, be relied upon to stall the air motor. The valve 24' is, however, useful for the purpose 01' closing the discharge passage 2! or the nozzle during the period that the mold is not in operation. Ii it is not desired to rely upon the back pressure to stall the air motor, the operating lever II of the control valve 50 in the fluid medium line ll may be operatively connected by a linkage 51' with the operating lever 26' of the valve M. This linkage may be so constructed and arranged as to cut oil the supply of fluid under pressure to the motor 48 when the valve 2k is closed and to open the valve 56 so as to supply fluid under pressure to the motor I when the valve 24 is open.

In operation of molding apparatus embodying my invention. the hopper is kept filled with solid particles of plastic-like material which may comprise particles of granular or dust sizes or larger particles of broken up scrap material. Mixtures of such particles may be successfully discharged by the improved plastic discharge mechanism for the reason that the customary close and precision 1 fitting relationship oi a piston and cylinder type pump is not required and the problem or avoiding scoring of such pump cylinders is not present. While only two displacing plungers are disclosed in the embodiment of the invention illus trated in the drawing, it should be understood that any number of such plungers may be em. played by providing a corresponding number of passageways such as the passageways II and 2! for their accommodation. A single plunger may be used particularly in the injection molding of small articles wherein molds of small capacity may be rapidly filled. The cooling or the locations at which the seals against reverse flow or plastic through the nozzle are provided enables the apparatus to remain idle for relatively long periods of time without resulting in breaking down of the cake-like formations of solid particles o! plastic-like material by subjecting them to softening temperatures. The speed of operte'rials, it may, as in conventional practice, be round desirable to cool the mold in order to solidity the injected oi the mold sections it and i3 audwlnle the charge is held under compression therein? In the molding of thermosetting materials inch require the application ot'heat m ordee oconvert them to a solid stste it may be found desirable to heat; thei'mold while the p stic is maintained under compression there- 'Moldsecticns which can be readily removed from the molding apparatus and placed in an oven in order to cure thermosetting material or rubber or rubber-like status may in some instances be used to advantage in speeding up the rate of molding articles with paratus.

The foregoingplastic discharge apparatus may be employed to project in a mobile state plastic materials or substantially all characters, including rubber compounds, through an extrusion die. In the extrusion oi cylindrical stock, for example, the discharge from the outlet 24 may be received by a suitable support or container (not shown) and heat cured or solidified by cooling or otherwise depending upon the properties of flieplastic material. 7

Although but one specific embodiment either invention isherein shown and described, it will be understood that various changes in the size, shape and arrangement 01' parts may be ,made githout departing from the spirit of the liver;-

I claim: 7

1. Injection apparatus for molding plastic-like materiai'lncluding a hopper for such material, a discharge nozzle, a pair of relatively short passageways connecting the interiors and needle, 9. pair of reciprocative displacing elements disposed in said hopper each in alinement with one of said passageways and each having a portion of its stroke in part of said hopper and the remaining portion in the passageway with which it is aligned respectively, and mechmism for alternately driving each of said displacing elements through a plurality of relatively short discharge strokes while the other element is returned from a previous discharge stroke to displace a substantially continuous stream-like discharge from said nozzle sulllcient to fill a mold of predetermined capacity said displacing elements and driving mechanism being so constructed and arranged with respect to said hopper and passageways that one of said elements traverses a substantial part of the hopper portion of its discharge stroke after the other element has been withdrawn from its passageway in order to agitate the material in said hopper and cause it to flow into said latter passageway. 1 2. Injecting apparatus for molding plastic-like material comprising a hopper for solid particles oi such material, an outlet passageway leading from said hopper having a portion adjacent the latter 01' smaller cross sectional area. than the next succeeding portion and having a shoulder between said portions of said passageway provided with a flat side facing away from said hopper and extending substantially at right angles to the well of said passageway, a reciproplastic material rapidly lie-- the foregoing apof said hopper" cable displacing element disposed in said hopper in allnement with said smaller portion oi said passageway and having relatively close iltting engagement with the wall thereof for iorcing particles or solid material therethrough and compressing the same into a cake-like formation, said cake-like formation being engageable with said flat side iorsealing said smaller portion oi said passageway against reverse iiow of said material therethrough, a nozzle having a discharge passage communicating with the end of said passageway remote from said hopper, and means for reciprocating said displacing element.

3. Injecting apparauis for discharging plasticlike material comprising a hopper for particles of such material, a pair of outlet passageways leading from said hopper, each having a portion adiacent the latter oi smaller cross sectional area than the next successive portion and each having a shoulder between the portions thereof of diiierent cross sectional area provided with a substantially flat side facing away from said hopper and extending substantially at right angles to the wall of the passageway, a pair oi reciprocative plungers disposed in said hopper each in alinement with one of said passageways and each having a portion of its stroke in part of said hopper and the remaining portion in the passageway with which it is allned respectively for forcing particles oi solid material therethrough and compressing the same into a cake-like i'ormation: said cake-like iormation being engageable with said flat side oi the shoulder oi one pasageway for sealing the smaller portion oi the latter against reverse how of said material therethrough during discharge of plastic-like material through the other passageway, a nozzle having a discharge passage communicating with said passageways, and driving mechanism for alternately propelling said plungers through their respective discharge strokes, said driving mechanism being adapted to propel one plunger through a portion of said hopper while the other plunger is displaced from its alined ay in order to agitate plastic-like material of said hopper into the latter passageway.

4. Apparatus for injecting plastic-like material comprising a hopper for such material, a nozzle passage and said hopper, means tor displacing said material from said hopper and i'orclng it through said noszle discharge passage, mechanism for driving said displacing means, a valve for controlling the flow oi plastic-like material through said nossle discharge passage, a control for said driving mechanism, and means interconnecting said valve and said driving mechanism control so constructed and arranged as to shirt the latter to render said driving mechanism operatlve and inoperative when said valve is opened and closed respectively.

5 Injection apparatus ior molding plasticmaterial including a hopper for such material, a discharge nozle, a relatively short passageway connecting the interiors oi said hopper and nozzle, a reclprocative displacing element disposed in said hopper in alignment with said passageway and having a portion of its displacing stroke in partoisaidhopperandtheremainingportion 01' its displacing stroke in said passageway, mechanism for driving said displacing element through a plurality oi relatively short reciprocations to displace a charge 0! plastic sufllcient to iill a mold or predetermined capacity, a valve at the outlet end of said n e for controlling the flow oi plastic-like mate therefrom, a control for said driving mechanism, and means interconnecting said ,valve and said driving mechanism control so constructed and arranged as to shiit the latter to render said driving mechanism operative and inoperative when said valve is opened and closed respectively.

6. Apparatus for injecting moldable material, comprisin a nozzle having a discharge passage, a passageway communicatlvely connected at one end with said discharge e and having an inlet i'or said material spaced from said end, means ior i'orcing said material through said passageway and nozzle discharge e under pressure, a valve for controlling the iiow oi said material through said nozzle discharge e, a memher for controlling said means, and mechanism interconnecting said valve and said control membersoconstmctedandarrangedastoshiitthe latter to render said moldable material forcing means operative and inoperative when said valve is opened and closed, respectively.

WALTER P. COUSINO. 

